71 
by Dw;_, and Dw;. An investigation can be performed in a similar 
way as was demonstrated above for points in the center line of the 
strip. Further the influence upon the elevations along the edges of the 
strip from the errors of the first model has to be taken into account. 
The expression (288) has to be completed with the term 
  
: h? 2» 3» 
V V2gqd: ^ 359 Tad (201) 
3.22. Error distribution after bridging 
We assume one planimetry and two elevation control points to be 
available in the first model (—1,0) and one planimetry and elevation 
control point in the last model (n,n + 1), see fig. 1. After an aerial 
triangulation on an approximate scale and levelling the entire strip is 
assumed to be transformed into the coordinate system of the ground 
with the aid of the planimetry control points. For the transformation 
in planimetry two translations, one rotation and one scale change of the 
entire strip are assumed to be used. The differential formulae of the 
transformation are demonstrated in the expressions (17) and (18). In 
elevation the transformation is assumed to be performed with the aid 
of the three elevation control points. For the transformation two 
rotations and one translation of the strip are assumed to be applied. 
The differential formula of the transformation is 
dh = dh, -- xd» + ydé (292) 
3.221. The x-coordinates 
The errors of the preliminarily triangulated x- coordinates of the last 
model with respect to the first model of the strip can be expressed by 
the formula (234) for the center line of the strip. 
The error in the second control point is corrected with the aid of the 
expression (17). The coordinates of the two control points are assumed 
to be 
= bn 
m=0 % 
(293) 
43,70 3,7390 
Consequently the corrections of the elements of the coordinate trans- 
formation are found from 
0 — — da, 
db (294) 
Dx — — dx, — bn 7 
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